An important component of the inflammatory process involves the migration and activation of select populations of leukocytes from the circulation and their accumulation in the affected tissue. While the idea of leukocyte trafficking is not new, it has enjoyed a renaissance recently following the discovery and characterization of the selectin and integrin families of adhesion molecules and the large family of selective chemotatic cytokines known as chemokines. Chemokine receptors are expressed on leukocytes and process the signals following the binding of the chemokine whereby such signals are eventually transduced into migration or activation of the leukocytes towards the source of the chemokine. Therefore, by regulating the migration and activation of leukocytes from the peripheral blood to extravascular sites in organs, skin, articulations or connective, tissue, chemokines play a critical role in the maintenance of host defense as well as in the development of the immune response.
Originally, the chemokine family of molecules was divided into two groups: the “C—X—C” subfamily and the “C—C” subfamily. The characteristic feature of both of these subfamilies is the presence of four cysteine residues in highly conserved positions in the molecules. In the “C—C” chemokine subfamily, the first two residues are adjacent to each other, while in the “C—X—C” subfamily, the cysteine residues are separated by a single amino acid residue. A recent description of a “—C—” chemokine appears to represent a new family of chemokines in that the “—C” chemokine lacks two of the four cysteine residues present in the “C—C” subfamily or the “C—X—C” subfamily.
One member of the “C—C” subfamily of chemokines is macrophage inflammatory protein-1α (“MIP-1α”). It is expressed by cells such as macrophages, T and B lymphocytes, neutrophils and fibroblasts. A recent study (see Karpus, W. J. et al., J. Immunol. (1995), Vol. 155, pp. 5003-5010) provides strong in vivo concept validation for a role of MIP-1α in a mouse experimental autoimmune encephalomyelitis (EAE) model of multiple sclerosis. Multiple sclerosis is an autoimmune disease mediated by T and B lymphocytes and macrophages, resulting in extensive inflammation and demyelination of white matter in the central nervous system. The study showed that antibodies to MIP-1α prevented the development of both initial and relapsing disease as well as preventing the infiltration of mononuclear cells into the central nervous system. Treatment with the antibodies was also able to ameliorate the severity of ongoing clinical disease. These results led the investigators to conclude that MIP-1α plays an important role in the etiology of multiple sclerosis. In addition, another study (see Godiska, R. et al., J. Neuroimmunology. (1995), Vol. 58, pp. 167-176) demonstrated an upregulation of mRNA for a number of chemokines, including MIP-1α, in the lesions and spinal cord of SJL mice (a strain of mice susceptible to Th1 diseases such as EAE) during the course of acute EAE.
RANTES is another member of the C—C chemokine subfamily (the name RANTES is an acronym derived from some of the original observed and predicted characteristics of the protein and its gene: Regulated upon Activation Normal T cell Expressed presumed Secreted). A wide variety of tissues have been found to express RANTES in a similar pattern to MIP-1α. Strong evidence exists linking RANTES to organ transplant rejection, particularly of the kidney. The infiltration of mononuclear cells into the interstitium of organ transplants is the hallmark of acute cellar rejection. This cellular infiltrate primarily consists of T cells, macrophages and eosinophils. In a study of RANTES expression during acute renal allograft rejection, RANTES mRNA expression was found in infiltrating mononuclear cells and renal tubular epithelial cells and RANTES itself was found to be bound to the endothelial surface of the microvasculature within the rejecting graft (see Pattison, J. et al., Lancet (1994), Vol. 343, pp. 209-211 and Wiedermann, C. J. et al., Curr. Biol. (1993), Vol. 3, pp. 735-739).
There is also evidence from a number of studies to implicate the abnormal production of RANTES in the progression of rheumatoid arthritis (see Rathanaswami, P. et al., J. Biol. Chem. (1993), Vol. 268, pp. 5834-5839 and Snowden, N. et al., Lancet (1994), Vol. 343, pp. 547-548). Rheumatoid arthritis is a chronic inflammatory disease characterized in part by a memory T lymphocyte and monocyte infiltration, which is believed to be mediated by chemotactic factors released by inflamed tissues.
In addition, there is strong evidence from other studies implicating RANTES in the pathophysiology of rheumatoid arthritis (see Barnes, D. A. et al., J. Clin. Invest. (1998, in press) and Plater-Zyberk, C. A. et al., Immunol. Lett. (1997), Vol. 57, pp. 117-120). For example, in an adjuvant-induced arthritis (AIA) model in the rat, antibodies to RANTES greatly reduced the development of disease in rats induced for AIA.
These studies and others provide strong evidence that MIP-1α levels are increased in EAE models of multiple sclerosis and that RANTES levels are increased in rheumatoid arthritis and kidney transplant rejection (see, e.g., Glabinski, A. R. et al., Am. J. Pathol. (1997), Vol. 150, pp. 617-630; Glabinski, A. R. et al., Methods. Enzymol. (1997), Vol. 288, 182-190; and Miyagishi, R. S. et al., J. Neuroimmunol. (1997), Vol. 77, pp. 17-26). In addition, as described above, these chemokines are chemoattractants for T cells and monocytes which are the major cell types that are involved in the pathophysiology of these diseases. Therefore, any molecule that inhibits the activity of either of these chemokines would be beneficial in treating these diseases and would therefore be useful as an anti-inflammatory agent.